Detecting for the presence of particular components may be useful for a variety of reasons. With respect to environmental concerns, an apparatus for detecting pollution or industrial emission, whether in the liquid or gaseous state, may alert an individual responsible for limiting such contaminants as to when a given quantity of pollution has entered water systems or the atmosphere. A gas detection unit may be used for detecting the presence of dangerous chemical compounds, such as carbon monoxide, in a mixture of gases. In the medical field, a gas detection unit may be used for detecting a particular gas in equipment, such as an oxygen inhalation machine, for alerting staff as to the amount of oxygen remaining in the reservoir or given to the patient.
Known methods and apparatuses have been developed to detect the presence of gases or liquids. Typical systems include gas chromatography, ion chromatography, electrolytic conductivity detection, and conductometric measurement. However, these detection systems have generally been expensive, cumbersome, or shown to have low sensitivities and slower response times. In situations where a generally quick response time may be desired, such as detecting toxic gases or a lack of oxygen in an oxygen inhalation machine, detection systems having enhanced abilities to quickly detect particular gases or liquids are usually favorable.
Systems for detecting gases appear to be disclosed in U.S. Pat. No. 4,843,016 to Fine, U.S. Pat. No. 5,268,302 to Rounbehler et al., U.S. Pat. No. 6,458,328 to Wreyford, and U.S. Pat. No. 5,152,963 to Wreyford. In these systems, a gas chromatograph column appears to be placed prior to the reactor so that components of the mixture may be separated from one another prior to being oxidized and/or reduced. This apparatus often permits particular compounds to be detected upon exiting the reactor. For example, a detector coupled to the reactor may be used to detect H2S while other compounds, such as H2O, CH4, SO2, or SO3, may not be detected by the detector.
However, if a total concentration of hydrogen is desired using the apparatuses shown in Fine, Rounbehler, or two Wreyford patents, multiple detectors may be needed to detect all of the compounds containing hydrogen, such as a detector for detecting H2O and another detector for CH4. The detectors' results may thereafter need to be summed, which may also introduce measurement error with respect to each detector, so that the total amount of hydrogen may be determined.
U.S. Pat. No. 4,293,308 to Sisti et al. (“Sisti”) appears to relate to a method and apparatus for determining a total concentration of sulfur in a gas sample. Sisti seems to teach a reactor for combusting a gas sample and oxygen, followed by a gas chromatograph column for separating components of the combustion mixture from one another. The separated components seem to then be conveyed to a known thermal conductivity detector (“TCD”) for detection.
FIG. 1 depicts a conventional TCD in accordance with the prior art. As shown, first, second, third, and fourth cells 1,2,3,4, respectively, appear to contain first, second, third and fourth heaters 1a, 2a, 3a, and 4a, respectively. Fluid being examined is typically led from an inlet 5a (see arrow) of the first cell 1, made to flow through first cell 1 and second cell 2, and led out of an outlet 5b (see arrow) of second cell 2. A reference fluid is usually led from an inlet 6a (see arrow) of third cell 3, made to flow through third cell 3 and fourth cell 4, and led out of an outlet 6b (see arrow) of fourth cell 4. In addition, first, second, third and fourth heaters 1a, 2a, 3a and 4a, are most often connected to form an electrical bridge 7 and a predetermined current is normally supplied from a constant current supply 8 to bridge 7.
When an unbalance voltage is generated in bridge 7, a detection circuit 9 may detect such unbalance voltage, and in that way, variation in thermal conductivity of the fluids being examined may be measured, wherein the variation may indicate the amount of a component present in a mixture.
However, TCDs may have limited detection capabilities. As described in U.S. Pat. No. 5,295,389 to Nagata (“Nagata”), TCDs seem to be adversely affected due to the flow of gases that are to be detected, resulting in inaccurate gas measurements.
Hence, the Sisti method and apparatus for detecting total sulfur concentration, due to the possible limitations of the detector, may have limited sensitivity and/or accuracy. Moreover, Sisti appears to relate to a method and apparatus that is limited to a determination of a single component and where a determination of multiple components may require multiple operations in succession.
What is desired, therefore, is an improved detection system that determines a total concentration of a component from a mixture of components. What is also desired is a detection system having enhanced sensitivity and accuracy. A further desire is a detection system that efficiently and contemporaneously detects total concentrations of multiple components. A still further desire is a detection system that efficiently detects total concentrations of multiple components while reducing interference from undesired components.